How clouds over the ocean affect our climate, and how climate change may be affecting THEM, is not well known. There is no network of observing stations like on land, and climate models have not been shown to really simulate clouds well. They may be just too fine a detail for models that cover such large scale phenomenon as oceanic circulation. But clouds over the oceans have been thought be important in our understanding of what drives our climate.

In a study published in the July 24 issue of Science, researchers Amy Clement and Robert Burgman from the University of Miami's Rosenstiel School of Marine and Atmospheric Science and Joel Norris from Scripps Institution of Oceanography at UC San Diego begin to unravel this mystery. Using observational data collected over the last 50 years and complex climate models, the team has established that low-level stratiform clouds appear to dissipate as the ocean warms, indicating that changes in these clouds may enhance the warming of the planet.The result of their analysis was a surprising degree of agreement between two multi-decade datasets that were not only independent of each other, but that employed fundamentally different measurement methods. One set consisted of collected visual observations from ships over the last 50 years, and the other was based on data collected from weather satellites.

ADVERTISEMENT

"The agreement we found between the surface-based observations and the satellite data was almost shocking," said Clement, a professor of meteorology and physical oceanography at the University of Miami and winner of the American Geophysical Union's 2007 Macelwane Award for her groundbreaking work on climate change. "These are subtle changes that take place over decades. It is extremely encouraging that a satellite passing miles above the earth would document the same thing as sailors looking up at a cloudy sky from the deck of a ship."Together, the observations and the Hadley Centre model results provide evidence that low-level stratiform clouds, which currently shield the earth from the sun's radiation, may dissipate in warming climates, allowing the oceans to further heat up, which would then cause more cloud dissipation.

"This is somewhat of a vicious cycle potentially exacerbating global warming," said Clement. "But these findings provide a new way of looking at cloud changes. This can help to improve the simulation of clouds in climate models, which will lead to more accurate projections of future climate changes. "